#!/usr/bin/python

"""Models wired and wireless interfaces."""

import logging
import os
import re
import subprocess

import experiment

METRIC_5GHZ = 20
METRIC_24GHZ_5GHZ = 21
METRIC_24GHZ = 22

RFC2385_MULTICAST_ROUTE = '239.0.0.0/8'

experiment.register('WifiSimulateWireless')
CWMP_PATH = '/tmp/cwmp'
MAX_ACS_FAILURE_S = 60


class Interface(object):
  """Represents an interface.

  Base class for more specific interface types.
  """

  CONNECTION_CHECK = 'connection_check'
  IP_ROUTE = ['ip', 'route']
  IP_ADDR_SHOW = ['ip', 'addr', 'show', 'dev']

  def __init__(self, name, base_metric):
    self.name = name
    self.logger = logging.getLogger(self.name)

    # Currently connected links for this interface, e.g. ethernet.
    self.links = set()

    # Whether [ACS, internet] access is currently available via this interface.
    self._has_acs = None
    self._has_internet = None

    self._subnet = None
    self._gateway_ip = None
    self.base_metric = base_metric
    self.metric_offset = 0

    # Until this is set True, the routing table will not be touched.
    self._initialized = False

  @property
  def metric(self):
    return str(int(self.base_metric) + self.metric_offset)

  def _connection_check(self, check_acs):
    """Check this interface's connection status.

    Args:
      check_acs:  If true, check for ACS access rather than internet access.

    Returns:
      Whether the connection is working.
    """
    # Until initialized, we want to act as if the interface is down.
    if not self._initialized:
      self.logger.info('not initialized; not running connection_check%s',
                       ' (ACS)' if check_acs else '')
      return None

    if not self.links:
      self.logger.info('Connection check failed due to no links')
      return False

    self.logger.debug('Gateway IP is %s', self._gateway_ip)
    if self._gateway_ip is None:
      self.logger.info('Connection check%s failed due to no gateway IP',
                       ' (ACS)' if check_acs else '')
      return False

    self.add_routes()
    if 'default' not in self.current_routes():
      return False

    cmd = ['timeout', '5', self.CONNECTION_CHECK, '-I', self.name]
    if check_acs:
      cmd.append('-a')

    with open(os.devnull, 'w') as devnull:
      result = subprocess.call(cmd, stdout=devnull, stderr=devnull) == 0
      self.logger.info('Connection check%s %s',
                       ' (ACS)' if check_acs else '',
                       'passed' if result else 'failed')

    return result

  def gateway(self):
    return self._gateway_ip

  def acs(self):
    if self._has_acs is None:
      self._has_acs = self._connection_check(check_acs=True)

    return self._has_acs

  def internet(self):
    if self._has_internet is None:
      self._has_internet = self._connection_check(check_acs=False)

    return self._has_internet

  def add_routes(self):
    """Update default routes for this interface.

    Remove any stale routes and add any missing desired routes.
    """
    if self.metric is None:
      self.logger.info('Cannot add route without a metric.')
      return

    # If the current routes are the same, there is nothing to do.  If either
    # exists but is different, delete it before adding an updated one.
    current = self.current_routes()

    to_add = []

    subnet = current.get('subnet', {})
    if self._subnet:
      if ((subnet.get('route', None), subnet.get('metric', None)) !=
          (self._subnet, str(self.metric))):
        self.logger.debug('Adding subnet route')
        to_add.append(('subnet', ('add', self._subnet, 'dev', self.name,
                                  'metric', str(self.metric))))
        subnet = self._subnet
    else:
      subnet = None
      self.delete_route('default', 'subnet')

    default = current.get('default', {})
    if self._gateway_ip:
      if (subnet and
          (default.get('via', None), default.get('metric', None)) !=
          (self._gateway_ip, str(self.metric))):
        self.logger.debug('Adding default route')
        to_add.append(('default',
                       ('add', 'default', 'via', self._gateway_ip,
                        'dev', self.name, 'metric', str(self.metric))))
    else:
      self.delete_route('default')

    # RFC2365 multicast route.
    if current.get('multicast', {}).get('metric', None) != str(self.metric):
      self.logger.debug('Adding multicast route')
      to_add.append(('multicast', ('add', RFC2385_MULTICAST_ROUTE,
                                   'dev', self.name,
                                   'metric', str(self.metric))))

    for route_type, _ in to_add[::-1]:
      self.delete_route(route_type)

    for _, cmd in to_add:
      self._ip_route(*cmd)

  def delete_route(self, *args):
    """Delete default and/or subnet routes for this interface.

    Args:
      *args:  Which routes to delete.  Must be at least one of 'default',
          'subnet', 'multicast'.

    Raises:
      ValueError:  If neither default nor subnet is True.
    """
    args = set(args)
    args &= set(('default', 'subnet', 'multicast'))
    if not args:
      raise ValueError(
          'Must specify at least one of default, subnet, multicast to delete.')

    # Use a sorted list to ensure that default comes before subnet.
    for route_type in sorted(list(args)):
      while route_type in self.current_routes():
        self.logger.debug('Deleting %s route', route_type)
        self._ip_route('del', self.current_routes()[route_type]['route'],
                       'dev', self.name)

  def current_routes(self):
    """Read the current routes for this interface.

    Returns:
      A dict mapping 'default' and/or 'subnet' to a dict containing the gateway
      [and metric] of the route.  Only contains keys for routes that are
      present.
    """
    result = {}
    for line in self._ip_route().splitlines():
      if 'dev %s' % self.name in line:
        if line.startswith('default'):
          route_type = 'default'
        elif re.search(r'/\d{1,2}$', line.split()[0]):
          route_type = 'subnet'
        else:
          continue
        route = {}
        key = 'route'
        for token in line.split():
          if token in ['via', 'metric']:
            key = token
          elif key:
            if key == 'route' and token == RFC2385_MULTICAST_ROUTE:
              route_type = 'multicast'
            route[key] = token
            key = None
        if route:
          result[route_type] = route

    return result

  def _ip_route(self, *args):
    if not self._initialized:
      self.logger.info('Not initialized, not running %s %s',
                       ' '.join(self.IP_ROUTE), ' '.join(args))
      return ''

    try:
      self.logger.debug('calling ip route %s', ' '.join(args))
      return subprocess.check_output(self.IP_ROUTE + list(args))
    except subprocess.CalledProcessError as e:
      self.logger.error('Failed to call "ip route" with args %r: %s', args,
                        e.message)
      return ''

  def _ip_addr_show(self):
    try:
      return subprocess.check_output(self.IP_ADDR_SHOW + [self.name])
    except subprocess.CalledProcessError as e:
      self.logger.error('Could not get IP address: %s', e.message)
      return None

  def get_ip_address(self):
    match = re.search(r'^\s*inet (?P<IP>\d+\.\d+\.\d+\.\d+)',
                      self._ip_addr_show(), re.MULTILINE)
    return match and match.group('IP') or None

  def set_gateway_ip(self, gateway_ip):
    self.logger.info('New gateway IP %s', gateway_ip)
    self._gateway_ip = gateway_ip
    self.update_routes(expire_cache=True)

  def set_subnet(self, subnet):
    self.logger.info('New subnet %s', subnet)
    self._subnet = subnet
    self.update_routes(expire_cache=True)

  def _set_link_status(self, link, is_up):
    """Set whether a link is up or not."""
    if is_up == (link in self.links):
      return

    had_links = bool(self.links)

    if is_up:
      self.logger.info('gained link %s', link)
      self.links.add(link)
    else:
      self.logger.info('lost link %s', link)
      self.links.remove(link)

    # If a link goes away, we may have lost access to something but not gained
    # it, and vice versa.
    if is_up != self._has_acs:
      self._has_acs = None

    if is_up != self._has_internet:
      self._has_internet = None

    if had_links != bool(self.links):
      self.update_routes(expire_cache=False)

  def expire_connection_status_cache(self):
    self.logger.debug('Expiring connection status cache')
    self._has_internet = self._has_acs = None

  def update_routes(self, expire_cache=True):
    """Update this interface's routes.

    If the interface has ACS or internet access, prioritize its routes.  If it
    doesn't but has a link, deprioritize the routes.  If it has no links, delete
    the routes.

    Args:
      expire_cache:  If true, force a recheck of connection status before
      deciding how to prioritize routes.
    """
    self.logger.debug('Updating routes')
    if expire_cache:
      self.expire_connection_status_cache()

    if self.acs() or self.internet():
      self.prioritize_routes()
    else:
      # If we still have a link, just deprioritize the routes, in case we're
      # wrong about the connection check.  If there's no actual link, then
      # really delete the routes.
      if self.links:
        self.deprioritize_routes()
      else:
        self.delete_route('default', 'subnet', 'multicast')

  def prioritize_routes(self):
    """When connection check succeeds, route priority (metric) should be normal.

    This is the inverse of deprioritize_routes.
    """
    if not self._initialized:
      return
    self.logger.info('routes have normal priority')
    self.metric_offset = 0
    self.add_routes()

  def deprioritize_routes(self):
    """When connection check fails, deprioritize routes by increasing metric.

    This is conservative alternative to deleting routes, in case we are mistaken
    about route not providing a useful connection.
    """
    if not self._initialized:
      return
    self.logger.info('routes have low priority')
    self.metric_offset = 50
    self.add_routes()

  def initialize(self):
    """Tell the interface it has its initial state.

    Until this is called, the interface won't run connection checks or touch the
    routing table.
    """
    self._initialized = True
    self.update_routes()


class Bridge(Interface):
  """Represents the wired bridge."""

  def __init__(self, *args, **kwargs):
    self._acs_autoprovisioning_filepath = kwargs.pop(
        'acs_autoprovisioning_filepath')
    super(Bridge, self).__init__(*args, **kwargs)
    self._moca_stations = set()

  @property
  def moca(self):
    return bool(self._moca_stations)

  @moca.setter
  def moca(self, is_up):
    self._set_link_status('moca', is_up)

  @property
  def ethernet(self):
    return 'ethernet' in self.links

  @ethernet.setter
  def ethernet(self, is_up):
    self._set_link_status('ethernet', is_up)

  def add_moca_station(self, node_id):
    if node_id not in self._moca_stations:
      self._moca_stations.add(node_id)
      self.moca = True

  def remove_moca_station(self, node_id):
    if node_id in self._moca_stations:
      self._moca_stations.remove(node_id)
      self.moca = bool(self._moca_stations)

  def prioritize_routes(self):
    """We only want ACS autoprovisioning when we're using a wired route."""
    super(Bridge, self).prioritize_routes()
    open(self._acs_autoprovisioning_filepath, 'w')

  def deprioritize_routes(self, *args, **kwargs):
    """We only want ACS autoprovisioning when we're using a wired route."""
    if os.path.exists(self._acs_autoprovisioning_filepath):
      os.unlink(self._acs_autoprovisioning_filepath)
    super(Bridge, self).deprioritize_routes(*args, **kwargs)

  def delete_route(self, *args, **kwargs):
    """We only want ACS autoprovisioning when we're using a wired route."""
    if os.path.exists(self._acs_autoprovisioning_filepath):
      os.unlink(self._acs_autoprovisioning_filepath)
    super(Bridge, self).delete_route(*args, **kwargs)

  def _connection_check(self, check_acs):
    """Support for WifiSimulateWireless."""
    failure_s = self._acs_session_failure_s()
    if (experiment.enabled('WifiSimulateWireless')
        and failure_s < MAX_ACS_FAILURE_S):
      self.logger.info('WifiSimulateWireless: failing bridge connection check%s'
                       ' (no ACS contact for %d seconds, max %d seconds)',
                       ' (ACS)' if check_acs else '', failure_s,
                       MAX_ACS_FAILURE_S)
      return False

    return super(Bridge, self)._connection_check(check_acs)

  def _acs_session_failure_s(self):
    """How long have we been failing to connect to the ACS?

    Returns:
      The number of seconds between the last attempted ACS session and the last
      successful ACS session.
    """
    contact = os.path.join(CWMP_PATH, 'acscontact')
    connected = os.path.join(CWMP_PATH, 'acsconnected')

    if not os.path.exists(contact) or not os.path.exists(connected):
      return 0

    return os.stat(contact).st_mtime - os.stat(connected).st_mtime


class Wifi(Interface):
  """Represents a wireless interface."""

  def __init__(self, *args, **kwargs):
    self.bands = kwargs.pop('bands', [])
    super(Wifi, self).__init__(*args, **kwargs)
    # When the interface is reset (e.g. due to a firmware crash), we need to
    # force-restart wpa_supplicant next time we run "wifi setclient", even if
    # the config hasn't changed.
    self.recently_reset = False

  @property
  def wpa_supplicant(self):
    self.update()
    return 'wpa_supplicant' in self.links

  @wpa_supplicant.setter
  def wpa_supplicant(self, is_up):
    self._set_link_status('wpa_supplicant', is_up)

  def wpa_status(self):
    """Parse the STATUS response from the wpa_supplicant control interface.

    Returns:
      A dict containing the parsed results, where key and value are separated by
      '=' on each line.
    """
    status = {}

    try:
      lines = subprocess.check_output(['wpa_cli', '-i', self.name,
                                       'status']).splitlines()
    except subprocess.CalledProcessError:
      self.logger.error('wpa_cli status request failed')
      return {}

    for line in lines:
      if '=' not in line:
        continue
      k, v = line.strip().split('=', 1)
      status[k] = v

    return status

  def update(self):
    self.wpa_supplicant = self.wpa_status().get('wpa_state', '') == 'COMPLETED'

  def connected_to_open(self):
    status = self.wpa_status()
    return (status.get('wpa_state', None) == 'COMPLETED' and
            status.get('key_mgmt', None) == 'NONE')

  def current_secure_ssid(self):
    """Returns SSID if connected to a secure network, False otherwise."""
    status = self.wpa_status()
    return (status.get('wpa_state', None) == 'COMPLETED' and
            # NONE indicates we're on a provisioning network; anything else
            # suggests we're already on the WLAN.
            status.get('key_mgmt', None) != 'NONE' and
            status.get('ssid'))


class FrenzyWifi(Wifi):
  """A WPACtrl for Frenzy devices.

  Implements the same functions used on the normal WPACtrl, using a combination
  of the QCSAPI and wifi_files.  Keeps state in order to generate events by
  diffing saved state with current system state.
  """

  def _qcsapi(self, *command):
    try:
      return subprocess.check_output(['qcsapi'] + list(command)).strip()
    except subprocess.CalledProcessError as e:
      self.logger.error('QCSAPI call failed: %s: %s', e, e.output)
      raise

  def wpa_status(self):
    """Generate and cache events, update state."""
    try:
      client_mode = self._qcsapi('get_mode', 'wifi0') == 'Station'
      ssid = self._qcsapi('get_ssid', 'wifi0')
      security = (self._qcsapi('ssid_get_authentication_mode', 'wifi0', ssid)
                  if ssid else None)
    except subprocess.CalledProcessError:
      # If QCSAPI failed, don't crash.
      return {}

    up = bool(client_mode and ssid)
    self.wpa_supplicant = up

    if up:
      return {
          'wpa_state': 'COMPLETED',
          'ssid': ssid,
          'key_mgmt': security or 'NONE',
      }
    else:
      return {
          'wpa_state': 'SCANNING',
      }